At First Things, Joe Carter argues that brevity is the essential quality of the horror genre. That’s because:

Sustaining the emotions of fear, dread, or dismay is often difficult and uncomfortable; the quicker the audience can move through the cycle of tension-release-catharsis, the more visceral the impact and powerful the effect of the story. This is why the master’s of horror literature (e.g., Edgar Allen Poe, Shirley Jackson) almost always used the form of the short story.

Mr. Carter is not a fan of the modern horror filmmaking. He says that it’s ineffective because the emotional experience of horror must be briefer than a modern feature-length film. That’s why, he argues, some of the best horror filmmaking can be found in public service announcements, most of which are under a minute long.

In his blog post, Mr. Carter embeds videos of several examples, all of which are terrifying enough to justify a content warning—especially if you look at them as encounters with dark, supernatural forces.